Hanlin Wang

Flexible, Low‐Voltage and High‐Performance Polymer Thin‐Film Transistors and Their Application in Photo/Thermal Detectors

X. T. Liu, Prof. Y. Q. Ma College of Science China Agricultural University Beijing 100193 , P. R. China E-mail: mayongqiang@cau.edu.cn Dr. Y. L. Guo, Dr. H. J. Chen, Z. P. Mao, H. L. Wang, Prof. G. Yu, Prof. Y. Q. Liu Beijing National Laboratory for Molecular Sciences Institute of Chemistry Chinese Academy of Sciences Beijing 100190 , P. R. China E-mail: guoyunlong@iccas.ac.cn; yugui@iccas.ac.cn; liuyq@iccas.ac.cn

High‐Performance, Air‐Stable Field‐Effect Transistors Based on Heteroatom‐Substituted Naphthalenediimide‐Benzothiadiazole Copolymers Exhibiting Ultrahigh Electron Mobility up to 8.5 cm V−1 s−1

Rational heteroatom engineering is applied to develop high-performance electron-transporting naphthalenediimide copolymers. Top-gate field-effect transistors fabricated from selenophene-containing polymers achieve an ultrahigh electron mobility of 8.5 cm2 V-1 s-1 and excellent air-stability. The results demonstrate that the incorporation of selenophene heterocycles into the polymers can improve the film-forming ability, intermolecular interaction, and carrier transport significantly.

Substrate‐Free Ultra‐Flexible Organic Field‐Effect Transistors and Five‐Stage Ring Oscillators

Freestanding, substrate-free organic field-effect transistors and organic circuits with a nominal thickness of 320 nm are demonstrated by using a simple water-floatation method. The devices work well in freestanding status, attached on banknotes, or bent over the blade of a knife. The ultralight devices with extreme bending stability indicate a bright future for organic electronics.

Inkjet Printing Short‐Channel Polymer Transistors with High‐Performance and Ultrahigh Photoresponsivity

Inkjet-printed short-channel polymer transistors exhibit a high performance (μavg = 1.20 cm(2) V(-1) s(-1) ). With a 50 μm orifice nozzle, polymer transistors with a sub-micrometer (700 nm) channel length are mass-fabricated with good uniformity and reproducibility. In addition, owing to the device geometry, an ultrahigh photoresponsivity up to 10(6) A W(-1) is achieved, which realizes economical, lithography-free photodetectors.

Organic printed photonics: From microring lasers to integrated circuits.

Flexible organic photonic devices for high-performance optical information processing can be produced via ink-jet printing. A photonic integrated circuit (PIC) is the optical analogy of an electronic loop in which photons are signal carriers with high transport speed and parallel processing capability. Besides the most frequently demonstrated silicon-based circuits, PICs require a variety of materials for light generation, processing, modulation, and detection. With their diversity and flexibility, organic molecular materials provide an alternative platform for photonics; however, the versatile fabrication of organic integrated circuits with the desired photonic performance remains a big challenge. The rapid development of flexible electronics has shown that a solution printing technique has considerable potential for the large-scale fabrication and integration of microsized/nanosized devices. We propose the idea of soft photonics and demonstrate the function-directed fabrication of high-quality organic photonic devices and circuits. We prepared size-tunable and reproducible polymer microring resonators on a wafer-scale transparent and flexible chip using a solution printing technique. The printed optical resonator showed a quality (Q) factor higher than 4 × 105, which is comparable to that of silicon-based resonators. The high material compatibility of this printed photonic chip enabled us to realize low-threshold microlasers by doping organic functional molecules into a typical photonic device. On an identical chip, this construction strategy allowed us to design a complex assembly of one-dimensional waveguide and resonator components for light signal filtering and optical storage toward the large-scale on-chip integration of microscopic photonic units. Thus, we have developed a scheme for soft photonic integration that may motivate further studies on organic photonic materials and devices.

Bis-Diketopyrrolopyrrole Moiety as a Promising Building Block to Enable Balanced Ambipolar Polymers for Flexible Transistors

A bis-diketopyrrolopyrrole (DPP dimer, 2DPP) core is synthesized with much stronger electron deficiency than DPP by homocoupling of DPP. 2DPP-based polymers, P2DPP-BT, P2DPP-TT, P2DPP-TVT, and P2DPP-BDT, are obtained. Top-gated organic field-effect transistors on plastic substrate are fabricated. Compared with their mono-DPP-based polymers, remarkable improvement of electron mobilities of P2DPPs is achieved. Meanwhile, their p-channel performance becomes higher.

Three-Component Integrated Ultrathin Organic Photosensors for Plastic Optoelectronics

By three-component integration, an integrated organic photosensor is presented using common organic dyes as building blocks. Gray-scale photosensing and signal amplification are achieved in the device within a wide range of light intensities. Moreover, with ultrathin film techniques, 470 nm thick devices are realized and continue to work when harshly bent.

Van der Waals Epitaxial Growth of Atomic Layered HfS2 Crystals for Ultrasensitive Near-Infrared Phototransistors

As a member of the group IVB transition metal dichalcogenides (TMDs) family, hafnium disulfide (HfS2 ) is recently predicted to exhibit higher carrier mobility and higher tunneling current density than group VIB (Mo and W) TMDs. However, the synthesis of high-quality HfS2 crystals, sparsely reported, has greatly hindered the development of this new field. Here, a facile strategy for controlled synthesis of high-quality atomic layered HfS2 crystals by van der Waals epitaxy is reported. Density functional theory calculations are applied to elucidate the systematic epitaxial growth process of the S-edge and Hf-edge. Impressively, the HfS2 back-gate field-effect transistors display a competitive mobility of 7.6 cm2 V-1 s-1 and an ultrahigh on/off ratio exceeding 108 . Meanwhile, ultrasensitive near-infrared phototransistors based on the HfS2 crystals (indirect bandgap ≈1.45 eV) exhibit an ultrahigh responsivity exceeding 3.08 × 105 A W-1 , which is 109 -fold higher than 9 × 10-5 A W-1 obtained from the multilayer MoS2 in near-infrared photodetection. Moreover, an ultrahigh photogain exceeding 4.72 × 105 and an ultrahigh detectivity exceeding 4.01 × 1012 Jones, superior to the vast majority of the reported 2D-materials-based phototransistors, imply a great promise in TMD-based 2D electronic and optoelectronic applications.

A Retina-Like Dual Band Organic Photosensor Array for Filter-Free Near-Infrared-to-Memory Operations

Human eyes use retina photoreceptor cells to absorb and distinguish photons from different wavelengths to construct an image. Mimicry of such a process and extension of its spectral response into the near-infrared (NIR) is indispensable for night surveillance, retinal prosthetics, and medical imaging applications. Currently, NIR organic photosensors demand optical filters to reduce visible interference, thus making filter-free and anti-visible NIR imaging a challenging task. To solve this limitation, a filter-free and conformal, retina-inspired NIR organic photosensor is presented. Featuring an integration of photosensing and floating-gate memory modules, the device possesses an acute color distinguishing capability. In general, the retina-like photosensor transduces NIR (850 nm) into nonvolatile memory and acts as a dynamic photoswitch under green light (550 nm). In doing this, a filter-free but color-distinguishing photosensor is demonstrated that selectively converts NIR optical signals into nonvolatile memory.

Alkylphenyl Substituted Naphthodithiophene: A New Building Unit with Conjugated Side Chains for Semiconducting Materials

In this article, a versatile 2-D conjugated polymer, PNDTP-DPP, containing alkylphenyl substituted naphthodithiophene is synthesized and characterized. PNDTP-DPP exhibits good solubility and crystallinity with a π-π stacking distance of ≈3.7 Å. Investigation of polymer solar cells (PSCs) and organic field-effect transistors (OFET) demonstrates a promising power conversion efficiency (PCE) of 4.11% and a high hole mobility of up to 0.86 cm(2) V(-1) s(-1) , so this is one of the few examples of versatile polymers that show both good field-effect mobility and PCE.